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More Moon and Venus

StarDate:

December 30, 2010

If you want to learn about the water in your bathtub, you can gauge how clear it looks, or check to see if any steam is rising from its surface. Or you can put your hand above it to feel its warmth. And after doing all that, you can get the best idea of all by sticking your toe in.

That's the stage a European spacecraft is at in its study of Venus. It's been examining the planet from a high orbit, using sophisticated instruments to probe Venus's thick, hot atmosphere. And now, it's sticking its toe in. It's dipping closer to Venus with each orbit around the planet -- close enough to pass through the outer fringes of its atmosphere.

Venus Express arrived at Venus four and a half years ago. It's revealed new details about the composition and structure of the planet's atmosphere. It's also discovered lightning in the clouds, and hints of volcanic activity on the surface.

The craft follows a highly elliptical orbit around Venus. Several times over the last couple of years, it's dipped as low as 100 miles above the surface. That's low enough to feel the effects of the upper atmosphere, which is only about half as thick as expected.

Eventually, Venus Express may drop as low as 75 miles -- low enough to use the atmosphere to alter its orbit. The maneuvers will reveal even more about Venus's complex atmosphere.

Look for Venus a little to the upper left of the crescent Moon at dawn tomorrow. It's the brilliant "morning star."

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